Changes in RationalTest.java

Correct the error I previously made in (exercism#2886)
no important files changed

exercises/practice/rational-numbers/src/test/java/RationalTest.java

@@ -11,7 +11,7 @@ public class RationalTest {
     private static final double DOUBLE_EQUALITY_TOLERANCE = 1e-15;
 
     private void assertDoublesEqual(double x, double y) {
-        assertThat(x).isEqualTo(y, within(DOUBLE_EQUALITY_TOLERANCE));
+        assertThat(x).isCloseTo(y, within(DOUBLE_EQUALITY_TOLERANCE));
     }
 
     // Tests